Although the meanings of the following acronyms are well understood by skilled artisans, the following list is deemed to assist in a better understanding of the invention:
3GPPthird generation partnership projectAAA authentication, authorization, and accountingAPaccess pointCCF charging control functionCSCFcall state control functionEIR equipment identity registerGGSNgateway GPRS support nodeGMSCgateway MSCGPRSgeneral packet radio systemGSMglobal system for mobile communicationHLRhome location registerHSShome subscriber serverIPinternet protocolIWMSCinterworking MSC for SMSMMSmulti-media servicesMSmobile stationMSCmobile switching stationPDGpacket data gatewayPHYphysical layerPDApersonal digital assistantSCservice centerSIMsubscriber identity moduleSMSshort messaging serviceTCPtransmission control protocolUMTS universal mobile telecommunications systemVOLPvoice over internet protocolWAGwireless application gatewayWATwireless access technologyWLANwireless local area networkWTRUwireless transmit/receive unit
The trend in the wireless industry is to increasingly support wireless transmit/receive units (WTRUs) that support multiple Wireless Access Technologies (WATs) in heterogeneous networks. Network interworking introduces the possibility of several WATs (e.g., several different types of wireless local area networks) such 802.11a, 802.11b, 802.11g, etc. being connected to a cellular type network (e.g., a Universal Mobile Telecommunications System (UMTS) network). Further, using subscriber identity module (SIM) technology, users may switch their 802.11b card to an 802.11a card, for example, or any other type of multi-mode card using their SIM to access the network while the network is not totally aware of the WAT supported at the WTRU level. Additionally, users may use their 802.11 cards, for example, in different types of WTRUs, such as when they obtain a new laptop or personal digital assistant (PDA), for example.
In light of the above, it is desirable to efficiently handle various types of wireless services across multiple WATs for WTRUs that may operate in cellular and WLAN type networks.